<script>
  {
    class TestClass { };
    const instance = new TestClass();
    console.assert(typeof instance === 'object');
  }
  {
    { class Inside { } }
    { class Inside { } }
    console.assert(typeof Inside === 'undefined');
  }
  {
    class User {
      constructor(id) {
        this.id = id
      }
    }
    const user = new User(42);
    console.assert(user.id, 42);
  }
  {
    class User {
      writesTests() {
        return false
      }
    }
    const 我不是测试员 = new User();
    console.assert(我不是测试员.writesTests() === false);
  }
  {
    class User {
      写测试() { this.写过任何一个测试 = true; }
      is懒惰() {
        if (this.写过任何一个测试) {
          return false
        }
        return true
      }
    }
    const 测试员 = new User();
    console.assert(测试员.is懒惰() === true);
    测试员.写测试();
    console.assert(测试员.is懒惰() === false);
  }
  {
    const classType = typeof {};
    console.assert(classType, 'function');
  }
</script>